Cortical Projection Topography of the Human Splenium: Hemispheric Asymmetry and Individual Differences

Abstract

The corpus callosum is the largest white matter pathway in the human brain. The most posterior portion, known as the splenium, is critical for interhemispheric communication between visual areas. The current study employed diffusion tensor imaging to delineate the complete cortical projection topography of the human splenium. Homotopic and heterotopic connections were revealed between the splenium and the posterior visual areas, including the occipital and the posterior parietal cortices. In nearly one third of participants, there were homotopic connections between the primary visual cortices, suggesting interindividual differences in splenial connectivity. There were also more instances of connections with the right hemisphere, indicating a hemispheric asymmetry in interhemispheric connectivity within the splenium. Combined, these findings demonstrate unique aspects of human interhemispheric connectivity and provide anatomical bases for hemispheric asymmetries in visual processing and a long-described hemispheric asymmetry in speed of interhemispheric communication for visual information.

The corpus callosum in primates: processing speed of axons and the evolution of hemispheric asymmetry

“…The posterior region of the CC includes the splenium which is involved in synchronizing visual information between the two hemispheres [34]. Recent neuroimaging studies in humans suggest that different regions within the splenium provide interhemispheric connectivity of dorsal visual and association parietal areas, posterior cingulate and retrosplenial cortices, and ventral visual areas [20,35,36]. Thus, the importance of more rapid conduction times for visuospatial information may reflect the need to preserve the interhemispheric integration of such information.…”

“…Previous studies of CC axon distributions have included samples from either a relatively small number of species [8,17 -19], a restricted region of the CC [20], or a broad comparative assembly of phylogenetically distant relatives [16]. To our knowledge, no investigation of axon size distributions among different regions of the CC has been conducted with a representative sample of species across primate phylogeny.…”

Long‐term acclimatization to high‐altitude hypoxia modifies interhemispheric functional and structural connectivity in the adult brain

“…The results found here were in line with previous studies that interindividual differences exist in splenial connectivity, and homotopic connections between the primary visual cortices are variable (Putnam et al. 2010). The distribution of the individuals with detected tracts were comparable between the two groups (Chi‐square = 0.034, P  =   1).…”

The second face of blindness: Processing speed deficits in the intact visual field after pre- and post-chiasmatic lesions

“…Further, because of the extensive interhemispheric connectivity in the visual system [56,57], areas within the intact hemisphere that are mirror-symmetrically located to the lesion are likely to suffer functional deficits because their transcallosal input is lost. After a unilateral visual cortex lesion the activity patterns of the seemingly ''unaffected'' hemisphere were found to be altered [50,52,58].…”